JP5051998B2 - Method for producing lower olefin - Google Patents

Description

  The present invention is a method for producing a lower olefin from a raw material gas containing dimethyl ether using a zeolite catalyst, which suppresses the deactivation of the zeolite catalyst and effectively suppresses the deactivation of the regenerated zeolite catalyst. The present invention relates to a method for producing a lower olefin to be obtained.

  Conventionally, a method of converting dimethyl ether or a mixture of dimethyl ether and methanol into a lower olefin containing ethylene and propylene by performing a dehydration reaction by contacting with a zeolite catalyst is known.

  In this method, the dehydration reaction is continuously carried out while supplying a raw material gas containing dimethyl ether to the zeolite, but the precipitated carbonaceous material adheres to the pore surface of the zeolite over time, making it effective for the reaction. Since the active site which acts is poisoned, there is a problem that the zeolite catalyst is gradually deactivated (temporary deactivation). Therefore, it is necessary to repeat the operation of regenerating the zeolite catalyst with reduced activity and restoring the activity.

For this reason, from the viewpoint of the production efficiency and cost of lower olefins, it has been studied to improve the life of the zeolite catalyst by suppressing the decrease in catalyst activity over time.
Here, inactive deactivation includes permanent deactivation as described later in addition to the temporary deactivation described above. Temporary deactivation is poisoning of catalytic active sites due to carbonaceous accumulation and can be regenerated by air calcination. On the other hand, permanent deactivation is the disappearance of active sites due to dealumination due to exposure to steam or heat, and regeneration is impossible due to irreversible structural changes.

In producing a lower olefin from methanol and dimethyl ether (DME) in the presence of a zeolite catalyst,
It is considered that the reaction proceeds sequentially through the route of methanol → dimethyl ether → olefin → aromatic compound → carbonaceous material to generate carbonaceous material. In order to suppress the formation of carbonaceous matter due to such a reaction and to suppress the deterioration of the catalyst due to thermal damage, it is desirable to prevent an excessive increase in temperature of the catalyst layer, and the removal of reaction heat is effective. . The removal of reaction heat is also important from the viewpoint of operating the apparatus safely. For this reason, various methods have been proposed in order to reduce the temperature rise of the catalyst layer.

For example, before introducing into a reactor for producing lower olefins, a method is adopted in which a reactor for converting methanol into dimethyl ether is installed in advance, and the reaction is divided into two stages to reduce the rise in catalyst layer temperature. Yes. Further, a method of reducing the temperature rise by adding a dilution gas to the raw material gas is also employed. For example, Patent Document 1 discloses hydrogen, helium, nitrogen, carbon dioxide, C ₁ -C ₇ saturation as the dilution gas. An example of adding 2 to 20 times the amount of hydrocarbon to the methanol raw material is shown.

By diluting the raw material gas and reducing the raw material gas partial pressure, not only can the temperature rise of the catalyst layer be suppressed, but the generated olefins can be further prevented from reacting sequentially, which also improves the yield of lower olefins. It is known that it may contribute, and a method using a large amount of steam as a dilution gas is widely adopted. In commercial processes, it is necessary to place a separation process after the olefin production reactor, but steam is easier to separate than other dilution gases, and water is produced as a by-product due to the dehydration reaction of the raw material gas. Therefore, the fact that it can be recycled and used is also a factor in the demand for using steam as a diluent gas. For example, Patent Document 2 describes that a lower olefin is produced at a steam partial pressure of 40 to 80 vol% in the feed.

  However, the addition of high-concentration steam alleviates carbonaceous precipitation and extends the time until the zeolite catalyst is temporarily deactivated, but there is a problem that sufficient catalyst activity and life cannot be obtained after regeneration. This is presumably because the skeletal aluminum forming the active site of the catalyst is desorbed from the zeolite skeleton structure due to the presence of steam, causing non-renewable deactivation (permanent deactivation).

  In addition to the steam generated in the reactor that converts methanol to dimethyl ether installed in the previous stage of the reactor for producing lower olefins as described above, steam is generated when additional steam is added as a dilution gas. Therefore, a large amount of evaporation energy is required to reduce the thermal efficiency of the entire process. In addition, since a facility for generating steam is required, the configuration of the apparatus becomes complicated and the process construction cost increases. There is also a problem that the operation of the apparatus becomes complicated.

  Further, improvement of the catalyst has been studied as another method for suppressing the temporary deactivation of the catalyst due to carbonaceous deposition. For example, a method is known in which the density of active sites on the catalyst is reduced by increasing the Si / Al ratio in ZSM-5 or by poisoning part of the acid sites by supporting a basic metal. ing.

  However, even if any of these methods is adopted, the decrease in activity (temporary deactivation) due to the deposition of carbonaceous matter on the catalyst over time is unavoidable, and the catalyst is regenerated by periodically burning and removing carbon. There is a need.

  In such a situation, the carbonaceous deposition on the catalyst is suppressed and the time until the temporary deactivation of the zeolite catalyst is lengthened. The permanent deactivation of the catalyst is small, and the regenerated catalyst has a sufficient activity for a long time. The emergence of a method for producing a lower olefin from a raw material containing dimethyl ether, which can be produced at a low cost and in a low yield, in particular, in a high yield, has been strongly desired.

  The present applicant has already proposed a method for reducing the amount of accumulated carbon by adding carbon dioxide to a raw material gas containing dimethyl ether (see Patent Document 3). In this method, gasification of the precipitated carbonaceous material with carbon dioxide gas is thought to reduce the accumulation of carbonaceous matter on the catalyst, and without promoting permanent deactivation of the catalyst, Precipitation is suppressed and the regeneration cycle of the catalyst is prolonged.

As a result of further diligent research, the recycle gas is used as the dilution gas, and the amount of steam in the feed gas circulated through the catalyst layer and the amount of C ₄ and / or C ₅ olefin are controlled finely onto the catalyst. It has been found that it is possible to effectively suppress temporary deactivation due to precipitation of carbonaceous carbon, to reduce permanent deactivation due to dealumination, and to economically produce lower olefins with a high yield of propylene. The invention has been completed.
U.S. Pat. No. 4,083,888 Special table 2003-535069 gazette Japanese Patent Laying-Open No. 2005-104912

The present invention suppresses carbonaceous deposition on the catalyst to lengthen the time until the temporary deactivation of the zeolite catalyst and suppresses the permanent deactivation of the catalyst, thereby economically collecting lower olefins, particularly propylene. Ingredients containing dimethyl ether that can be manufactured efficiently, reduce the amount of water recycled, increase process thermal efficiency, and eliminate the need for water recycling and steam generation or significantly reduce size and simplify operations It is an object of the present invention to provide a method for producing a lower olefin from the above.

The method for producing a lower olefin of the present invention comprises a raw material gas containing dimethyl ether and a diluent gas, and a feed gas having a steam ratio in the total amount in the range of 5 to 30 vol% is introduced into the olefin production reactor, A raw material gas is contacted with a zeolite catalyst in a reactor to produce a hydrocarbon product containing C _{2 to} C ₅ olefins, and propylene and, if necessary, ethylene are separated from the obtained hydrocarbon product. It is characterized in that at least a part of the recovered and separated propylene and optionally ethylene from the hydrocarbon product is used as at least a part of the dilution gas.

In the method for producing a lower olefin of the present invention, it is preferable to use a plurality of olefin production reactors connected in series, in parallel, or a combination thereof.
In the method for producing a lower olefin of the present invention, the raw material gas is preferably a gas containing dimethyl ether and methanol.

  In the method for producing a lower olefin of the present invention, the molar fraction of dimethyl ether and methanol (dimethyl ether: methanol) in the raw material gas is preferably in the range of 6: 0 to 6: 5.

In the method for producing a lower olefin of the present invention, the dilution gas contains C ₄ and / or C ₅ olefin derived from a residue obtained by separating propylene and, if necessary, ethylene from the hydrocarbon product, The ratio of the total amount of C ₄ and / or C ₅ olefin in the diluent gas to the total amount of methanol and dimethyl ether in the solvent is 0.3 to 5.0 in terms of a carbon-based molar ratio, and the olefin production reaction The ratio of the dilution gas excluding steam to the raw material gas introduced into the vessel (number of moles of dilution gas excluding steam / number of moles of carbon based on the raw material gas) is in the range of 0.2 to 5.0. preferable.

In the method for producing a lower olefin of the present invention, the zeolite catalyst preferably has an MFI structure.
In the method for producing a lower olefin of the present invention, the atomic ratio of silicon to aluminum (Si / Al) in the zeolite catalyst is preferably in the range of 50 to 300 in molar ratio.

  Further, in the method for producing a lower olefin of the present invention, the zeolite catalyst contains an alkaline earth metal M, and the atomic ratio (M / Al) of the alkaline earth metal M and aluminum in the zeolite catalyst is 0. It is preferably 5 or more.

  According to the method for producing a lower olefin of the present invention, the carbonaceous deposition on the catalyst is suppressed and the time until the temporary deactivation of the zeolite catalyst is lengthened, and the permanent deactivation of the catalyst is less and economically high. With a propylene selectivity, a lower olefin can be produced with good yield from a raw material containing dimethyl ether. Furthermore, by reducing the amount of water recycled, the thermal efficiency of the process can be increased, and the equipment related to water recycling and steam generation can be eliminated or greatly reduced in size and simplified in operation.

Hereinafter, the present invention will be specifically described.
In the method for producing a lower olefin of the present invention, a raw material gas containing dimethyl ether is used.
In the olefin production reactor in contact with a zeolite catalyst to convert hydrocarbon product containing C ₂ -C ₅ olefins.

  The raw material gas used in the present invention may be a gas containing dimethyl ether, may contain only dimethyl ether as a reaction component, or may contain dimethyl ether and methanol. As such a raw material gas, it is also preferable to use a gas containing methanol and dimethyl ether, which is obtained as a crude product when dimethyl ether is produced from methanol.

In the raw material gas used in the present invention, the molar fraction of dimethyl ether and methanol (dimethyl ether: methanol) in the raw material gas is preferably in the range of 6: 0 to 6: 5.
In the present invention, any catalyst that can convert dimethyl ether into a lower olefin can be used as the catalyst, but a zeolite catalyst having an MFI structure such as ZSM-5 is preferably used. Zeolite may contain oxides other than silica and alumina in its crystal structure. In addition, the zeolite catalyst used in the present invention preferably has an atomic ratio (Si / Al) between silicon and aluminum in the catalyst in the range of 50 to 300, preferably 50 to 200.

  The zeolite catalyst used in the present invention contains an alkaline earth metal M such as calcium or strontium, and the atomic ratio (M / Al) between the alkaline earth metal M and aluminum in the catalyst is 0.5 or more in molar ratio. , Preferably 0.75-15, more preferably 2-8. Such a zeolite catalyst containing an alkaline earth metal M can be prepared by a known method, and for example, can be suitably prepared by the method described in JP-A-2005-138000.

  Here, the atomic ratios Si / Al and M / Al are obtained by a conventional analysis method such as atomic absorption analysis or inductively coupled plasma emission analysis, or silicon-containing compounds used for the synthesis of the zeolite. And the stoichiometric ratio between the aluminum-containing compound and the stoichiometric ratio between the compound containing the alkaline earth metal M and the aluminum-containing compound.

  The reaction for converting dimethyl ether, or dimethyl ether and methanol into a lower olefin is carried out by introducing a raw material gas together with a diluent gas into an olefin production reactor filled with a zeolite catalyst and bringing the raw material gas into contact with the zeolite catalyst. The olefin production reactor may be a fixed bed, a moving bed, or a fluidized bed.

  In the present invention, in the feed gas, that is, in all the gaseous components introduced into the olefin production reactor, the ratio of steam is desirably in the range of 5 to 30 vol%, preferably 8 to 25 vol%. The amount of steam in such a feed gas is significantly smaller than that of a conventionally known method using a dilution gas containing steam, but it has the effect of suppressing the deposition of carbon on the surface of the zeolite catalyst. In addition, the permanent deactivation of the zeolite catalyst due to steam can be effectively suppressed.

  The olefin production reactor used in the present invention may be single or plural. When a plurality of olefin production reactors are used, the olefin production reactors can be connected in series, parallel, or a combination of these, for example, the reactors are used in series, and the raw material gas is processed in multiple stages. can do.

In the present invention, the feed gas means the sum of the raw material gas and the dilution gas. In the present invention, the raw material gas and the dilution gas may be mixed in advance and introduced into the olefin production reactor as a feed gas, or may be introduced separately. In the present invention, when there are a plurality of gas inlets to the olefin production reactor, or when a plurality of olefin production reactors are used in combination, the total of gaseous components introduced into the entire reaction system is the feed gas. is there.

  In the case of using a plurality of olefin production reactors, the ratio of steam in the feed gas introduced into the entire reaction system may be in the range of 5 to 30 vol%, and in the feed gas introduced into individual olefin production reactors. Although the ratio of the steam is not particularly limited, it is preferable that the ratio of the steam in the feed gas introduced into each reactor is in the range of 5 to 30 vol%.

In the present invention, when a lower olefin is produced using a plurality of olefin production reactors connected in series, preferably, a raw material gas containing dimethyl ether is dividedly introduced into each reactor, and the most upstream reactor Into each reactor, the feed gas is brought into contact with the zeolite catalyst and converted to a hydrocarbon product containing C _{2 to} C ₅ olefins. Here, the hydrocarbon product obtained in the upstream reactor is sequentially introduced into the downstream reactor, and propylene and, if necessary, ethylene are separated and recovered from the hydrocarbon product obtained from the most downstream reactor. In addition, at least a part of the residue obtained by separating propylene and ethylene as necessary can be used as at least a part of the dilution gas. At this time, it is preferable that the ratio of the steam contained in the total amount is 5 to 30 vol% with respect to the total amount (feed gas) of all the raw material gases and dilution gas introduced into each reactor.

Here, as shown in the schematic flow of FIG. 2, it is a case where a lower olefin is produced using a two-stage olefin production reactor connected in series, and dimethyl ether or the like is added to the most upstream olefin production reactor 1. The raw material gas (1) and the diluting gas (3) which is the recycle gas are supplied, and the hydrocarbon product containing the C ₂ -C ₅ olefin obtained in the reactor 1 is introduced into the reactor 2 downstream in the whole amount. At the same time, in the reaction system in which the raw material gas (2) is additionally supplied to the downstream reactor 2, the sum of (1), (2), and (3) corresponds to the feed gas in the present invention. At this time, since the hydrocarbon product obtained in the reactor 1 contains steam generated as a by-product in the dehydration reaction in which C _{2 to} C ₅ olefin is obtained from dimethyl ether (or dimethyl ether and methanol), it is introduced into the reactor 2. The steam ratio in the total amount can be easily controlled to 5 to 30 vol% with respect to the feed gas when viewed with respect to each of the reactor 1 and the reactor 2 without newly adding steam.

Further, in the case of producing lower olefins using two olefin production reactors connected in parallel as shown in the schematic flow of FIG. 3, dimethyl ether is respectively added to the olefin production reactors 1 ′ and 2 ′. downstream the feed gas (1 ') or (2', etc.), supplying a dilution gas (3 ') is a recycle gas, a hydrocarbon product containing C ₂ -C ₅ olefins obtained in each reactor In the separation and purification system, propylene (or ethylene and propylene) is separated, and at least a part of the separated residue is used as a dilution gas (3 ′). At this time, the feed gas defined in the present invention is the total of the raw material gases (1 ′), (2 ′) and the dilution gas (3 ′). In the flow of FIG. 3, separation and purification of hydrocarbon products are performed collectively, but in a system using a plurality of olefin production reactors in parallel, separation of each hydrocarbon product obtained from each olefin production reactor. Purification may be performed separately.

  In the present invention, when a plurality of olefin production reactors are used, the reaction conditions in each reactor, the type and amount of the catalyst, the feed gas supply amount, the ratio of the raw material gas to the dilution gas in the feed gas, etc. What is necessary is just to select according to a production amount etc., and may differ in each olefin production reactor.

In the present invention, the feed gas and the zeolite catalyst are contacted in the olefin production reactor, and a hydrocarbon product containing a C _{2 to} C ₅ olefin is obtained from the olefin production reactor.

The reaction conditions such as the feed rate of the raw material gas and diluent gas to the olefin production reactor, the gas pressure and the reaction temperature are appropriately set in consideration of the yield of the desired lower olefin and the catalyst life. In the present invention, 55% or more (carbon conversion) of the introduced raw material gas can be finally converted to propylene by appropriately setting the type of zeolite and the reaction conditions. From the viewpoint of the yield of the lower olefin and the life of the zeolite catalyst, it is preferable to set the flow rate of the raw material gas so that the WHSV (weight time space velocity) is 0.025 to 5 h ⁻¹ , more preferably. 0.1 to 3 h ⁻¹ .

  The pressure during the reaction is preferably 0.005 to 1.5 MPa, more preferably 0.02 to 1.0 MPa as the partial pressure of the raw material gas. Moreover, reaction temperature becomes like this. Preferably it is 350-750 degreeC, More preferably, it is 400-650 degreeC.

  From the obtained hydrocarbon product, ethylene and propylene or only propylene is separated and recovered as a product. In the present invention, if desired, components other than ethylene and / or propylene may be separated and recovered from the hydrocarbon product. Separation and recovery of ethylene and / or propylene from the hydrocarbon product can be performed by a known method, for example, by fractional distillation.

The residue obtained by separating ethylene and / or propylene from the hydrocarbon product contains light paraffin such as methane, C ₄ and C ₅ olefins, and aromatic compounds. In the present invention, at least a part of this residue is used as at least a part of the dilution gas described above. That is, in the present invention, the residue obtained by separating propylene and, if necessary, ethylene from the hydrocarbon product may be recycled as it is and introduced into the olefin production reactor as a diluent gas. May be used separately. When only propylene is separated and recovered from the hydrocarbon product, the ethylene in the residue may be recycled as it is and used as a diluent gas, or converted to a hydrocarbon having 4 or more carbon atoms such as dimerization. It may be used as a part of the dilution gas.

Further, in the present invention, the total amount of the dilution gas may be derived from a residue obtained by separating propylene and ethylene as necessary from the hydrocarbon product, and may contain the residue and other gases. . In the present invention, a component derived from a recycle gas, that is, a residue obtained by separating propylene and, if necessary, ethylene from a hydrocarbon product, is preferably 50 vol% or more, preferably about 60 to 90 vol% of the dilution gas. It is preferable to use a diluent gas contained in In the present invention, since a dilution gas in which the amount of steam and the amount of C ₄ and / or C ₅ olefins are controlled in detail is used, the amount of water recycled can be reduced by minimizing the dilution of the raw material gas by steam. The process thermal efficiency is increased and economical.

In the present invention, the dilution gas may be used according to the composition and amount of the raw material gas so that the ratio of the steam in the total amount of the feed gas is 5 to 30 vol%, but preferably the steam with respect to the raw material gas is excluded. It is desirable that the ratio of the dilution gas be used in such an amount that the range is 0.2 to 5.0 in terms of the number of moles of the dilution gas excluding steam / the number of moles of the source gas based on carbon. Further, with respect to the total amount of methanol and dimethyl ether in the feed gas, the total amount of C ₄ and C ₅ olefins in a diluent gas (total amount of methanol and dimethyl ether in the C ₄ and C ₅ olefins of the total amount / feed gas in the diluted gas) Preferably, the carbon-based molar ratio is in the range of 0.3 to 5.0. When a feed gas that satisfies such a relationship between the source gas and the dilution gas is used, carbonaceous precipitation on the surface of the zeolite catalyst is effectively suppressed without adding a large amount of steam, and the catalyst is temporarily deactivated. Can be extended, and permanent deactivation due to desorption of aluminum in the framework structure from the zeolite catalyst can be effectively suppressed.

  In such a method for producing a lower olefin of the present invention, when the zeolite catalyst that has been temporarily deactivated is regenerated, the zeolite catalyst exhibits a high catalytic activity equivalent to that at the time of first use, and the surface of the zeolite catalyst even after regeneration. Precipitation of carbonaceous matter is effectively suppressed, and lower olefins can be produced continuously for a long time. Propylene selectivity means the ratio of the amount of propylene produced in the total amount of hydrocarbon products (carbon basis) obtained in the entire reaction system per unit time. That is, the propylene selectivity in the hydrocarbon product can be expressed by the following formula.

  However, in the present invention, the hydrocarbon product means the total amount of the fraction obtained from the outlet of the olefin production reactor. Therefore, the “total hydrocarbon product” includes the components obtained in the reaction and unreacted or in this reaction. Both inactive ingredients are included. For this reason, the propylene selectivity obtained by the above formula is not strictly the selectivity of propylene in the lower olefin obtained by the reaction, but the propylene selectivity in the lower olefin produced by the reaction is higher.

EXAMPLES Hereinafter, the present invention will be described more specifically based on examples, but the present invention is not limited to these examples.

  In this example and comparative example, the catalyst life is measured as the time from the start of the reaction until the conversion of the raw material dimethyl ether becomes zero, and a mixed gas using dimethyl ether and nitrogen gas at 1: 1 is used. When the feed gas was used (Comparative Example 1), it was expressed as a relative value when the catalyst life time at the time of using a new (first use) zeolite catalyst was 1.00.

<Preparation of zeolite catalyst>
A zeolite raw material solution consisting of 9.50 g of A1 (NO ₃ ) ₃ .9H ₂ O and 10.92 g of Ca (CH ₃ COO) ₂ .H ₂ O was dissolved in 750 g of water. 500 g of Cataloid Si-30 water glass (manufactured by Catalysts & Chemicals), 177.5 g of 6 mass% NaOH aqueous solution, 317.6 g of 21.3% by mass tetrapropylammonium bromide aqueous solution, zeolite seed crystal 15.0 g of ammonium-type MFI structure zeolite (Zeolyst, Si / Al atomic ratio is 70) with an average particle size of 0.5 μm (corresponding to 10% by mass of the amount of zeolite catalyst synthesized without adding seed crystals) Amount) was added with stirring to give an aqueous gel mixture.

Subsequently, this aqueous gel mixture was put into a 3 L autoclave container, and hydrothermal synthesis was performed by stirring at 160 ° C. for 18 hours under an autogenous pressure.
The white solid product produced by hydrothermal synthesis was filtered and washed with water, dried at 120 ° C. for 5 hours, and calcined in air at 520 ° C. for 10 hours.

The calcined product was immersed in 0.6N hydrochloric acid and stirred at room temperature for 24 hours to make the zeolite type proton type.
Thereafter, the product was filtered and washed with water, dried at 120 ° C. for 5 hours, and calcined in air at 520 ° C. for 10 hours to obtain a proton type alkaline earth metal-containing MFI zeolite catalyst.

In the obtained zeolite catalyst, the Si / Al atomic ratio was 100, the Ca / Al atomic ratio was 3.7, the specific surface area was 320 m ² / g, and the average particle size was 1.5 μm.
<Production of lower olefin>
A feed gas composed of the components shown in Table 1 in which dimethyl ether (DME) as a raw material gas and a diluent gas composed of nitrogen, steam and isobutene are joined to a fixed bed flow reactor filled with the catalyst prepared above. The olefin production reaction was continuously carried out. The reaction conditions were normal pressure, reaction temperature of 530 ° C., and the weight-based space velocity (WHSV), which is the ratio of the feed amount of dimethyl ether per unit time to the catalyst unit amount, was 9.5 g-DME / (1 g-catalyst · hour). It was. Here, the dilution gas is a simulated recycle gas containing isobutene corresponding to the olefin component, nitrogen gas corresponding to a component inert to the reaction for producing the lower olefin, and steam.

The outlet gas from the reactor was subjected to component analysis by a gas chromatograph. Further, the catalyst life until the temporary deactivation is expressed as a relative life when a catalyst life of Comparative Example 1 described later using a new catalyst after the catalyst preparation and introducing a feed gas not containing isobutene and steam is assumed to be 1. did.

  The results are shown in Table 1.

  The catalyst used in Example 1 and having reached the catalyst life was calcined in an air stream at 550 ° C. for 10 hours to regenerate the catalyst, and the obtained regenerated catalyst was used. Similarly, lower olefins were produced. The results are shown in Table 1.

Comparative Example 1
In Example 1, using a mixed gas of dimethyl ether 50 vol% as a feed gas and nitrogen 50 vol% as a dilution gas, lower olefin production and component analysis of the reactor outlet gas were performed in the same manner as in Example 1. It was. The results are shown in Table 1.

Comparative Example 2
The catalyst used in Comparative Example 1 and having reached the catalyst life was calcined in an air stream at 550 ° C. for 10 hours to regenerate the catalyst, and the obtained regenerated catalyst was used. Similarly, lower olefins were produced. The results are shown in Table 1.

Comparative Example 3
In Example 1, a mixed gas containing 42 vol% of dimethyl ether as a feed gas and 34 vol% of nitrogen and 24 vol% of isobutene as a diluting gas was used as a feed gas in the same manner as in Example 1, and production of lower olefin and reactor outlet gas The component analysis of was performed. The results are shown in Table 1.

Comparative Example 4
The catalyst used in Comparative Example 3 and having reached the catalyst life was calcined in an air stream at 550 ° C. for 10 hours to regenerate the catalyst, and the obtained regenerated catalyst was used. Similarly, lower olefins were produced. The results are shown in Table 1.

Comparative Example 5
In Example 1, a mixed gas containing 25 vol% of dimethyl ether as a feed gas and 50 vol% of nitrogen and 25 vol% of nitrogen as a diluent gas was used as the feed gas, and production of lower olefin and reactor outlet gas were conducted in the same manner as in Example 1. The component analysis of was performed. The results are shown in Table 1.

Comparative Example 6
The catalyst used in Comparative Example 5 and having reached the catalyst life was calcined in an air stream at 550 ° C. for 10 hours to regenerate the catalyst, and the obtained regenerated catalyst was used. Similarly, lower olefins were produced. The results are shown in Table 1.

Comparative Example 7
In Example 1, a mixed gas containing 33 vol% of dimethyl ether as a feed gas and 32 vol% of nitrogen and 35 vol% of steam as a diluent gas was used as the feed gas, and the production of lower olefins and reactor outlet gas were performed in the same manner as in Example 1. The component analysis of was performed. The results are shown in Table 1.

Comparative Example 8
The catalyst used in Comparative Example 7 and having reached the catalyst lifetime was calcined in an air stream at 550 ° C. for 10 hours to regenerate the catalyst, and the obtained regenerated catalyst was used. Similarly, lower olefins were produced. The results are shown in Table 1.

From the above examples and comparative examples,
Comparison of Comparative Example 1 in which the raw material gas was diluted with nitrogen alone and Comparative Example 5 in which the raw material gas was diluted with steam. When the raw material gas was diluted with steam, the catalyst life (time until temporary deactivation due to carbonaceous deposition) It can be seen that increases significantly. Further, in Comparative Example 7 in which the steam addition concentration is further increased, the catalyst life is further increased, so that it can be seen that the catalyst life is increased in proportion to the steam concentration. On the other hand, from the results of Comparative Examples 1 and 2, Comparative Examples 5 and 6, and Comparative Examples 7 and 8, when the steam concentration in the feed gas is set to 30 vol% or more, the time until the regenerated catalyst is deactivated is drastically shortened. It is shown that the presence of a high concentration of steam causes permanent deactivation in which Al is irreversibly desorbed from the framework structure of the zeolite catalyst and the active sites are reduced. On the other hand, from Examples 1 and 2, in the present invention in which the amount of steam and the amount of C ₄ olefin in the feed gas are in specific ranges, the life of the catalyst at the first use is greatly prolonged, and the regenerated catalyst In the case of using the catalyst, the catalyst life is equivalent to that at the first use, and it is shown that the time until the temporary deactivation can be greatly prolonged with almost no permanent deactivation.

In Comparative Example 3 in which the raw material gas was diluted with isobutene, which is a C ₄ olefin, the catalyst life increased as in the case of the steam addition, and no shortening of the life was confirmed in Comparative Example 4 after catalyst regeneration. However, when the relative lifetimes of Example 1 and Comparative Example 3 and the relative lifetimes of Example 2 and Comparative Example 4 are compared, the relative lifetimes of Example 1 and Example 2 are larger, and steam is present in isobutene. The use of a dilution gas with an appropriate amount has an effect of extending the relative life of the catalyst.

  Further, in Examples 1 and 2, since it is not necessary to use a large amount of steam as a dilution gas, the thermal efficiency of the process is increased by reducing the amount of water recycled, and the equipment related to water recycling and steam generation is eliminated or Since significant downsizing can be achieved, the operating cost and construction cost can be greatly reduced.

FIG. 1 shows a schematic view of an embodiment when one olefin production reactor is used. FIG. 2 shows a schematic view of an embodiment when two olefin production reactors connected in series are used. FIG. 3 shows a schematic diagram of an embodiment when two olefin production reactors connected in parallel are used.

Claims (7)

A feed gas consisting of a raw material gas containing dimethyl ether and a dilution gas, with a steam ratio in the total amount in the range of 5 to 30 vol%, is introduced into the olefin production reactor,
The raw material gas is brought into contact with a zeolite catalyst in the reactor to produce a hydrocarbon product containing C ₂ -C ₅ olefins,
From the resulting hydrocarbon product, propylene and optionally ethylene is separated and recovered,
A method for producing a lower olefin, characterized in that at least a portion of the residue obtained by separating propylene and, if necessary, ethylene from the hydrocarbon product, is used as at least a portion of the dilution gas ;
The diluent gas comprises C ₄ and / or C ₅ olefins derived from the residue of propylene and optionally ethylene separated from the hydrocarbon product ;
The ratio of the total amount of C ₄ and / or C ₅ olefin in the diluent gas to the total amount of methanol and dimethyl ether in the raw material gas is 0.3 to 5.0 in terms of a carbon-based molar ratio, and
The ratio of the dilution gas excluding steam to the feed gas introduced into the olefin production reactor (number of moles of dilution gas excluding steam / number of moles of carbon based on feed gas) is in the range of 0.2 to 5.0. A process for producing a lower olefin.   The method for producing a lower olefin according to claim 1, wherein a plurality of olefin production reactors connected in series, in parallel, or a combination thereof are used.   The method for producing a lower olefin according to claim 1 or 2, wherein the source gas is a gas containing dimethyl ether and methanol.   4. The production of a lower olefin according to claim 1, wherein the molar fraction of dimethyl ether and methanol (dimethyl ether: methanol) in the raw material gas is in the range of 6: 0 to 6: 5. 5. Method.   The method for producing a lower olefin according to any one of claims 1 to 4, wherein the zeolite catalyst has an MFI structure.   The method for producing a lower olefin according to any one of claims 1 to 5, wherein the atomic ratio of silicon to aluminum (Si / Al) in the zeolite catalyst is in the range of 50 to 300 in terms of molar ratio. The zeolite catalyst contains an alkaline earth metal M, and an atomic ratio (M / Al) of the alkaline earth metal M and aluminum in the zeolite catalyst is 0.5 or more in terms of molar ratio. The manufacturing method of the lower olefin in any one of -6.

Images